Improvement: bulk creating new Orders

[martianatwork]

Basically when we are using bots we will be creating too many requests to the server. Previously we had a bulk order API, now as we have auth over ranger as well we can just use single websocket connection for orders Or bring back the multi order api to save a lot of resources

[mnaichuk]

@martianatwork we have it in backlog, maybe you can prepare PR?